This invention relates generally to semiconductor technology and more particularly to the method of forming liquid crystal displays (LCDs) having polycrystalline silicon regions within an amorphous silicon film, which overlies a display substrate.
Polycrystalline silicon is formed by crystallizing amorphous silicon films. One method of crystallizing amorphous silicon films is excimer laser annealing (ELA). Conventional ELA processes form polycrystalline films having a random polycrystalline structure. Random, as used here, means that no single crystal orientation is dominant and that polycrystalline structures consist of a mixture of crystallographic orientations in silicon. These crystallographic orientations in silicon are commonly denoted as  less than 111 greater than ,  less than 110 greater than , and  less than 100 greater than , along with their respective corollaries, as is well known in the art. Control of crystallographic orientation is generally desirable because the electrical characteristics of a polycrystalline silicon film depend upon the crystallographic orientation of the film. In addition, the uniformity of the electrical characteristics will improve if the majority of the film has a controllable texture.
ELA, as well as many other annealing methods, has not provided a means to control these microstructural characteristics and achieve a predictable and repeatable preferential crystal orientation and film texture within an annealed film.
It would be desirable to have a method of producing LCDs using a polycrystalline silicon film with a more uniform crystallographic orientation. It would also be desirable to be able to produce LCDs using predominantly  less than 100 greater than  polycrystalline silicon to form circuit structures or pixel structures.
Accordingly, a method of forming liquid crystal display (LCD) structures on a substrate, which has a polycrystalline silicon film with a desired predominant crystal orientation, is provided. The method of forming the LCD structures comprises the steps of: providing a substrate, depositing an amorphous silicon film on the substrate, annealing the substrate to produce a polycrystalline film region with the desired predominant crystal orientation, preferably a  less than 100 greater than  crystal orientation, forming pixel structures over the amorphous silicon film, and forming circuit structures over a polycrystalline film region.
Pixel structures, as well as, circuit structures include thin film transistors (TFTs), resistors, capacitors, or other structures that are formed using polycrystalline silicon.
The substrate is preferably a transparent substrate such as quartz, glass or plastic.
To achieve a good quality film that is predominantly  less than 100 greater than  crystal orientation, the step of depositing the amorphous film should deposit to a thickness of at least approximately 100 nm.
The step of annealing preferably uses a laterally-seeded excimer laser annealing process.
In another embodiment, the pixel region is formed over a polycrystalline silicon film region. In this embodiment, a circuit region need not be present. However, in a preferred embodiment both the pixel region and the circuit region are formed using a polycrystalline silicon film.
In a preferred embodiment, the polycrystalline region is polished to a thickness of less than approximately 60 nm. In some cases due to large substrate size, polishing may not be cost effective. In this case, using a film with a thickness greater than 100 nm will be a suitable compromise.
The method of the present invention, produces a liquid crystal display structure comprising at least one polycrystalline film region, which has a predominantly  less than 100 greater than  crystal orientation, overlying a substrate. A pixel region is formed using either amorphous silicon or the at least one polycrystalline film region. In a preferred embodiment, a circuit region is formed using the at least one polycrystalline film region.